This chapter discusses the principles of quality assurance (QA) and provides a discussion of techniques that can be used to train personnel to QA requirements. Starting with the definition of QA and its counterparts, quality control (QC) and quality improvement, the chapter then moves into a description of general QA program components. Quality assurance is not new to environmental microbiology. However, with the emphasis in environmental sciences being the detection of chemical contaminants and resulting engineered solutions (e.g., Superfund), environmental quality assurance (QA) program requirements have focused on the chemistry and engineering fields. Instructors employed to present the QA program can emphasize problem areas and are present to answer questions. The use of proceduralize scientific notebook, including organization, formatting, entry and attachment techniques, types of reviews, and archival protocols ensure uniform practices. Record-keeping requirements address the types of information to be documented, as well as the techniques to use. Sampling is an integral part of the study design. The selection of sampling sites and sampling strategies is based upon the study objectives and hypotheses. The second and third types of errors may be termed scientific misconduct and can have far-reaching effects, especially in the health fields, resulting in potential harm to humans at the worst and reflecting poorly on the research field at the least. The chapter defines and provides examples, when possible, of typical QA requirements that the environmental microbiologist might implement.